This invention relates to an induction system for an engine and more particularly to an air assisted fuel injection system for engines.
The use of fuel injection systems is becoming relatively commonplace, particularly in automotive applications. Fuel injection offers greater control of the fuel-air mixture than carburetors and thus offers improvements in both fuel economy and exhaust emission control. The fuel injector may inject fuel either directly into the combustion chamber or into the induction passage for induction along with the intake air into the combustion chamber. Regardless of which system is employed, it is desirable that the fuel delivered by the fuel injector is well atomized and mixed with the air.
Systems have been proposed wherein air under high pressure is injected along with the fuel. These systems are thought to improve fuel dispersion and atomization. However, the systems proposed for this purpose require relatively high air pressures and hence the engine must be provided with an air compressor, a drive for the air compressor and in many instances, regulation units for regulating the air pressure. The complexity of these systems at many times offsets their advantages.
Another type of system has been proposed, particularly for induction system injection, wherein air at substantially atmospheric pressure is employed in conjunction with the fuel injector to disperse and atomize the fuel. For example, if the fuel injector is positioned in the induction system close to the engine intake port, the fuel is injected frequently at a time when the air pressure in the intake port is substantially less than atmospheric. Thus, if atmospheric air can be introduced in proximity to the fuel injector, this air will be at a higher pressure than the surrounding air and the fuel can be dispersed and atomized.
Most of the systems proposed for this purpose have had substantial limitations. For example, if the system is employed in engines having multiple cylinders, the air assist is obtained from a manifold that interconnects all of the cylinders and hence the amount of air available per cylinder is substantially reduced.
In order to avoid this problem, distributor valves have been proposed so that air will be introduced at the cylinders in sequence. This increases the amount of air that is available, but has other disadvantages and limits the applicability of the system to meet varying conditions.
It is, therefore, a principal object of this invention to provide an improved air-assisted injection system.
It is a further object of this invention to provide an improved distributor valve for an air-assisted fuel injection system.
The air-assisted fuel injection systems previously proposed have been utilized for only the single purpose aforenoted. That is, the air assist has been employed only for the purpose of atomizing and mixing the fuel with the air. However, in accordance with a number of features of this invention, it has been discovered that the assist air may be utilized for a variety of additional purposes.
For example, it is possible through the use of air assist to vary the air assist and the way the air is added so as to control the direction at which the fuel charge enters the combustion chamber.
It is, therefore, a still further object of this invention to provide an air-assisted fuel injection system wherein the air assist is employed for controlling the direction of fuel flow into the combustion chamber of the engine.
In addition to controlling the direction of fuel flow, the air assist may be employed for achieving results in addition to the control and dispersion of the fuel. For example, with conventional engine induction systems in normally aspirated engines, there is a lag in the time period between when the intake valve opens and the intake charge actually flows into the combustion chamber. This is because the air in the induction passage is relatively stationary at the time the intake valve opens and it must be accelerated to a velocity to cause it to flow into the combustion chamber. This gives rise to loss of volumetric efficiency and pumping losses.
In accordance with another object of the invention, an air assist system is employed for introducing air into the combustion chamber immediately upon opening of the intake valve so as to avoid pumping losses and improve volumetric efficiency.
Closely related to the aforenoted problem is a condition which results in what is referred to as "internal EGR" (exhaust gas recirculation). Because of the fact that there is an overlap between the opening of the intake valve and the closing of the exhaust valve, the pressure in the combustion chamber may be higher than atmospheric at the time when the intake valve opens. Thus, rather than having a charge enter the combustion chamber through the intake valve, some of the exhaust gases may flow into the induction system through the open intake valve. As the pressure in the cylinder decreases, the charge which is drawn into the combustion chamber constitutes a fairly large percentage of exhaust gas and hence a condition a condition known as internal EGR exists. This obviously can be detrimental to running under some characteristics.
Therefore, it is a still further object of this invention to provide an air-assisted system for an engine wherein internal EGR may be controlled by introducing air at atmospheric pressure in the intake passage at the time the intake valve is open and when there is an overlap between the opening of the intake valve and the closing of the exhaust valve.
Another condition which presents difficulties in obtaining good engine performance is at idling. When the engine idles, the amount of air inducted is relative small and also is at a relatively low velocity. This causes a substantial reduction in turbulence in the combustion chamber and slow combustion. This, in turn, substantially reduces fuel economy and deteriorates exhaust emission control.
It is, therefore, a still further object of this invention to improve the idle operation of an engine by supplying a substantial portion of the idle air charged through the air assist system.
Normally the idle speed of an engine is controlled at least in part by either varying the position of the throttle valve or by controlling the air flow through an idle bypass passageway that extends around the throttle valve. These idle speed controlling methods generally result in rather poor idle speed running and idle speed control because of the fact that the adjustment of the idle air flow takes place a substantial distance away from the combustion chambers.
It is, therefore, a still further object of this invention to try to provide an improved method and apparatus for controlling idle speed through the use of an air assist system.
It has been previously noted that an important feature of the invention resides in the ability to use the air assist to control the direction of fuel flow into the combustion chamber. As has been noted, however, under certain circumstances, the air charge that enters the combustion chamber is at a low velocity and in low amounts. This gives rise to incomplete combustion and other associated problems.
It is, therefore, a still further object of this invention to employ an air assist system for an engine that can be employed for introducing turbulence into the combustion chamber under certain running conditions.
In addition to increasing the velocity of air flow into the combustion chamber to increase turbulence, it is also desirable to provide a system wherein the direction of air flow in the combustion chamber can be controlled. Various flow controlling systems have been proposed for this purpose. One disadvantage with such flow controlling systems is that in order to induce turbulence in the combustion chamber the intake passage is restricted and hence the high-speed performance of the engine can be deteriorated.
It is, therefore, a still further object of this invention to employ an air-assisted system for an engine where the air assist can be employed to generate the desired type of flow pattern in the combustion chamber depending upon the engine running condition.
As has been noted, one type of air assist system for multi-cylinder engines employs a sequentially operated valve for sequentially supplying air to the individual fuel injectors associated with each cylinder. Normally this type of sequential valve is driven in timed relationship with the engine camshaft. Such an arrangement, however, does not permit the attainment of a number of the objects which have been aforenoted.
It is, therefore, a still further object of this invention to provide an improved control valve for an air-assisted fuel injection system wherein the timing and duration of the air assist may be controlled.